Total body fat becomes depleted in both experimental animals and man with neoplastic disease. The present study examines a possible biochemical mechanism for this effect: stimulation of adipose tissue lipolysis. Epididymal fat pads from rats implanted i.p. or i.m. with the Walker 256 Carcinosarcoma had 2-4 times greater in vitro basal lipolytic rates (micron Eq FFA produced/g/h) than those from non-implanted controls. Adipose tissue lipolysis was significantly elevated starting at day 4-5 after transplanting the tumor i.p. and at day 7-10 after i.m. implantation. At both of these time periods the diseased rats were in good physical condition and free of anorexia. The i.p. tumor was usually fatal by day 7 and the i.m. tumor by day 21. Plasma FFA levels were consistently elevated in rats with the i.p. but not i.m. tumor. The cause of the increased fat mobilization in cancer is unknown. Possible explanations include increased sensitivity of adipose tissue to lypolytic agents and elaboration of lipolytic factors by the host or tumor. Lipolysis of fat pads from normal and tumor bearing rats was equally stimulated by norepinephrine. The cell-free ascites fluid from the peritoneal cavity of i.p. tumors and the blood serum from normal and tumor bearing rats are being examined for lipolytic factors. The goals of the research proposed for the final year of this grant are as follows: 1. To establish the identity and origin of the lipolytic factors present in cell-free ascites fluid. 2. To determine if the blood plasma or serum of tumor bearing rats contains increased amounts of lipolytic agents, and, if so, to determine their origin and identity. 3. To determine the source of the lipase enzymes present in the ascites fluid of the Walker 256 tumor and to compare this lipase with those seen before in this tumor.